Swift4.0 Codable + Realm (CodableでJsonをパース→RealmでDBに投入）

Kind.swift

//
//  Kind.swift
//  ExamRealm1
//
//  Created by Sakura on 2018/01/22.
//  Copyright © 2018年 Sakura. All rights reserved.
//

import Foundation
import RealmSwift

class Kind : RealmSwift.Object, Codable {
  @objc dynamic var id: Int = 0
  @objc dynamic var name: String?
  @objc dynamic var typeId: Int = 0

  enum CodingKeys: String, CodingKey {
    case id = "id"
    case name = "name"
    case typeId = "type_id"
  }

  required convenience init(from decoder: Decoder) throws {
    self.init()
    let values = try decoder.container(keyedBy: CodingKeys.self)
    id = (try values.decodeIfPresent(Int.self, forKey: .id))!
    name = try values.decodeIfPresent(String.self, forKey: .name)
    typeId = (try values.decodeIfPresent(Int.self, forKey: .typeId))!
  }

  override static func primaryKey() -> String? {
    return "id"
  }
}

kinds.json

{
  "kinds": [
    {
      "id": 1,
      "name": "穀類",
      "type_id": 1
    },
    {
      "id": 2,
      "name": "豆・種実・藻類",
      "type_id": 1
    },
    {
      "id": 3,
      "name": "いも・野菜・きのこ類",
      "type_id": 1
    },
    {
      "id": 4,
      "name": "果実類",
      "type_id": 1
    },
    {
      "id": 5,
      "name": "魚介類",
      "type_id": 1
    },
    {
      "id": 6,
      "name": "肉類",
      "type_id": 1
    },
    {
      "id": 7,
      "name": "卵・乳類",
      "type_id": 1
    },
    {
      "id": 8,
      "name": "油脂類・調味料・香辛料",
      "type_id": 1
    },
    {
      "id": 9,
      "name": "砂糖・ジャムなど",
      "type_id": 1
    },
    {
      "id": 10,
      "name": "主食（ごはん・パンなど）",
      "type_id": 2
    }
  ]
}

Kinds.swift

//
//  Kinds.swift
//  ExamRealm1
//
//  Created by Sakura on 2018/01/22.
//  Copyright © 2018年 Sakura. All rights reserved.
//

import Foundation

class Kinds : Codable {
  let kinds : [Kind]?

  enum CodingKeys: String, CodingKey {
    case kinds = "kinds"
  }

  required init(from decoder: Decoder) throws {
    let values = try decoder.container(keyedBy: CodingKeys.self)
    kinds = try values.decodeIfPresent([Kind].self, forKey: .kinds)
  }
}

ViewController.swift

//
//  ViewController.swift
//  ExamRealm1
//
//  Created by Sakura on 2018/01/19.
//  Copyright © 2018年 Sakura. All rights reserved.
//

import Foundation
import UIKit
import RealmSwift

class ViewController: UIViewController {

//  var realm: Realm!
  var kinds: [Kind]?

  override func viewDidLoad() {
    super.viewDidLoad()

    loadJsonFile()
    saveDB()
  }

  override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
  }

  func loadJsonFile() {
    guard let path = Bundle.main.path(forResource: "kinds", ofType: "json") else { return }
    let url = URL(fileURLWithPath: path)

    do {
      let data = try Data(contentsOf: url)
      let kinds = try JSONDecoder().decode(Kinds.self, from: data)

      for kind in (kinds.kinds)!{
        print("(json)kind.id:\(kind.id) name:\(kind.name ?? "null") typeId:\(kind.typeId)")
      }
      self.kinds = kinds.kinds

    } catch  {
      print(error)
    }
  }

  func saveDB() {
    let realm = try! Realm()

    try! realm.write {
      realm.deleteAll()
      for kind in self.kinds! {
        realm.add(kind)
      }
    }
    print(realm.objects(Kind.self))
  }
}